Balancing the strength and ductility of MnFeCoNi high-entropy alloy through regulating precipitates and nanostructures

Abstract

This study prepared MnFeCoNi high-entropy alloys with precipitates and high-density lattice defects (dislocations, stacking faults, deformation twins, etc.) using powder metallurgy combined with deep cryogenic deformation (DCD). The alloy demonstrates exceptional yield strength (1370 ± 56.64 MPa) and ultimate tensile strength (1463 ± 74.05 MPa), but exhibits limited elongation (3.18 %). Annealing the alloy at different temperatures enables microstructure evolution, allowing precise control over the morphology, quantity, and distribution of defects. This achieves an optimal balance between yield strength (1209 ± 30.88 MPa) and elongation rate (8.51 %). The results indicate that the outstanding mechanical properties of high entropy alloys primarily arise from the synergistic strengthening effect of its nano-spherical σ phase and high-density lattice defects, including dislocations, stacking faults, and deformation twins.